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40  structures 4793  species 3  interactions 4974  sequences 12  architectures

Family: SRP_SPB (PF02978)

Summary: Signal peptide binding domain

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Signal peptide binding domain Provide feedback

No Pfam abstract.

Literature references

  1. Clemons WM Jr, Gowda K, Black SD, Zwieb C, Ramakrishnan V; , J Mol Biol 1999;292:697-705.: Crystal structure of the conserved subdomain of human protein SRP54M at 2.1 A resolution: evidence for the mechanism of signal peptide binding. PUBMED:10497032 EPMC:10497032


External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR004125

The signal recognition particle (SRP) is a multimeric protein, which along with its conjugate receptor (SR), is involved in targeting secretory proteins to the rough endoplasmic reticulum (RER) membrane in eukaryotes, or to the plasma membrane in prokaryotes [PUBMED:17622352, PUBMED:16469117]. SRP recognises the signal sequence of the nascent polypeptide on the ribosome, retards its elongation, and docks the SRP-ribosome-polypeptide complex to the RER membrane via the SR receptor. Eukaryotic SRP consists of six polypeptides (SRP9, SRP14, SRP19, SRP54, SRP68 and SRP72) and a single 300 nucleotide 7S RNA molecule. The RNA component catalyses the interaction of SRP with its SR receptor [PUBMED:17507650]. In higher eukaryotes, the SRP complex consists of the Alu domain and the S domain linked by the SRP RNA. The Alu domain consists of a heterodimer of SRP9 and SRP14 bound to the 5' and 3' terminal sequences of SRP RNA. This domain is necessary for retarding the elongation of the nascent polypeptide chain, which gives SRP time to dock the ribosome-polypeptide complex to the RER membrane. In archaea, the SRP complex contains 7S RNA like its eukaryotic counterpart, yet only includes two of the six protein subunits found in the eukarytic complex: SRP19 and SRP54 [PUBMED:12364595].

This entry represents the M domain of the 54 kDa SRP54 component, a GTP-binding protein that interacts with the signal sequence when it emerges from the ribosome. SRP54 of the signal recognition particle has a three-domain structure: an N-terminal helical bundle domain, a GTPase domain, and the M-domain that binds the 7s RNA and also binds the signal sequence. The extreme C-terminal region is glycine-rich and lower in complexity and poorly conserved between species.

These proteins include Escherichia coli and Bacillus subtilis ffh protein (P48), which seems to be the prokaryotic counterpart of SRP54; signal recognition particle receptor alpha subunit (docking protein), an integral membrane GTP-binding protein which ensures, in conjunction with SRP, the correct targeting of nascent secretory proteins to the endoplasmic reticulum membrane; bacterial FtsY protein, which is believed to play a similar role to that of the docking protein in eukaryotes; the pilA protein from Neisseria gonorrhoeae, the homologue of ftsY; and bacterial flagellar biosynthesis protein flhF.

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Alignments

We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the NCBI sequence database, and our metagenomics sequence database. More...

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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

  Seed
(124)
Full
(4974)
Representative proteomes NCBI
(3784)
Meta
(2145)
RP15
(465)
RP35
(879)
RP55
(1145)
RP75
(1356)
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1Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: ✓ available, x not generated, not available.

Format an alignment

  Seed
(124)
Full
(4974)
Representative proteomes NCBI
(3784)
Meta
(2145)
RP15
(465)
RP35
(879)
RP55
(1145)
RP75
(1356)
Alignment:
Format:
Order:
Sequence:
Gaps:
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We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

  Seed
(124)
Full
(4974)
Representative proteomes NCBI
(3784)
Meta
(2145)
RP15
(465)
RP35
(879)
RP55
(1145)
RP75
(1356)
Raw Stockholm Download   Download   Download   Download   Download   Download   Download   Download  
Gzipped Download   Download   Download   Download   Download   Download   Download   Download  

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER3.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...

Trees

This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

Note: You can also download the data file for the tree.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Structural domain
Previous IDs: none
Type: Domain
Author: Griffiths-Jones SR
Number in seed: 124
Number in full: 4974
Average length of the domain: 100.10 aa
Average identity of full alignment: 43 %
Average coverage of the sequence by the domain: 21.33 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.1 20.1
Trusted cut-off 20.1 20.1
Noise cut-off 19.4 19.7
Model length: 104
Family (HMM) version: 14
Download: download the raw HMM for this family

Species distribution

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Interactions

There are 3 interactions for this family. More...

SRP54 SRP54_N SRP_SPB

Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the SRP_SPB domain has been found. There are 40 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.

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